MySQL GROUP_CONCAT: Formatting the output

Question

I currently have the following query:

SELECT group_concat(DISTINCT usrFirst, usrLast) as receiver_name  //etc

When using PHP, it outputs my list of names as follows:

<?php 
    echo $row['receiver_name'];

    //Outputs: JohnDoe,BillSmith,DaveJones

    //Desired output: John Doe, Bill Smith, and Dave Jones

I need help figuring out three things:

1. How can I put a space between the first and last name?

2. How can insert a space after each comma?

3. How can I add an 'and' right before the last name displayed?

Answer 1

I'm not sure you should bully MySQL into doing exactly what you want there. I'd suggest using the following:

SELECT DISTINCT CONCAT(first, ' ', last) AS receiver_name
FROM names;

Then loop through this resultset in PHP and handle the case of ' and ' there.

If performance is a concern (you'll be doing this query often). You would benefit from not using DISTINCT on the calculated value of CONCAT(first, ' ', last) as that would require the use of a temporary table.

To tweak it, add the following index:

ALTER TABLE names ADD INDEX (last, first);

And change your query as follows:

SELECT CONCAT(first, ' ', last) AS receiver_name
FROM names
GROUP BY last, first;

You'll be able to get your values directly from the index without resorting to a temporary table or filesort.

As far as the loop goes, something like the following would work:

<?php

$mysqli = new mysqli(/* connection info */);

$sql = "SELECT CONCAT(first, ' ', last) AS receiver_name "
     . 'FROM names '
     . 'GROUP BY last, first';

if ($result = $mysqli->query($sql)) {

    $string = '';
    $count = $result->num_rows;
    $rows = $result->fetch_all();
    for ($i = 0; $i < $count-1; $i++) {
        $string .= $rows[$i][0] . ', ';
    }
    $string .= ' and ' . $rows[$i][0];
    echo $string; // John Smith, Bob Dole, and George Bush
}

Note This code assumes you would always have at least 2 rows returned. I'm sure you can figure out how to handle the case of only a single name returned. :)

Answer 2

SELECT  GROUP_CONCAT(CONCAT_WS(' ', usrFirst, usrLast)) as receiver_name
FROM    (
        SELECT  DISTINCT usr_first, usr_last
        FROM    mytable
        ) q

This solution will distinguish between 'Smith, John Davis' and 'Davis Smith, John' (will return 'John Davis Smith' twice, not once, since they are different people).